The present invention relates, in general, to field emission displays, and, more particularly, to anode plates for high voltage field emission displays.
Field emission displays (FED""s) are known in the art. High voltage FED""s are operated at anode voltages that are greater than about 1000 volts. A typical high voltage anode plate includes a transparent substrate upon which is formed an anode, which typically is made from indium tin oxide. The cathodoluminescent phosphors are disposed on the anode.
It is also know to provide an aluminum layer on the cathodoluminescent phosphors in order to improve brightness. The aluminum layer improves the brightness of the display image by reflecting the light that is initially directed away from the viewer.
However, aluminum oxide (Al2O3), which is known to exist at the outer surface of the aluminum layer, readily forms hydrates. The water from the hydrates can be liberated into the vacuum of the FED when the aluminum layer is struck by the electron beams. Furthermore, it is known that aluminum oxide can be decomposed by electron bombardment, thereby evolving oxygen into the vacuum of the FED. It is known that the presence of water and oxygen are undesirable because they can react with the electron emitter structures, thereby contaminating them and causing deterioration of their emissive properties.
It is also known that adding layers to the electron-receiving surfaces of the cathodoluminescent phosphors has the undesirable effect of lowering the energy of the electrons. This problem is more pronounced in low voltage FED""s because the electrons are much less energetic when they arrive at the anode plate, as contrasted with high voltage FED""s. Thus, it is known in the art that the addition of layers at the electron-receiving side of the cathodoluminescent phosphors can be undesirable.
Accordingly, there exists a need for a field emission display, which overcomes at least these shortcomings of the prior art.